Radiation imagery chemistry: process – composition – or product th – Regenerating image processing composition
Patent
1994-02-01
1996-05-28
Bowers, Jr., Charles L.
Radiation imagery chemistry: process, composition, or product th
Regenerating image processing composition
430399, 430400, 430 30, 354298, G03C 500, G03C 300, G03C 518, G03C 526
Patent
active
055210554
DESCRIPTION:
BRIEF SUMMARY
This invention relates to improvements in or relating to photographic processing.
It is common practice in photofinishing laboratories to use a densitometer to measure the optical transmission and reflection densities of test strips of photographic materials which have been exposed to a well defined given level. These test strips are used to provide data with which the process, in both paper and film processors, is kept under control.
Many printers, particularly the more sophisticated ones which may be left unattended while working, are equipped with multipixel film scanners. These scanners are effectively high resolution densitometers which are capable of yielding density data which is later used by the exposure control algorithm of the printer to calculate the required exposure which must be given to the print being made from the negative being scanned.
It is known in the industry that a separate scanner may be attached to the end of either the film processor or paper processor, especially for black-and-white materials. This scanner is used to perform process control based on the density of the processed material.
It has also been realized that the printer's scanner is effectively an on-board densitometer which can be used to effect process control measurements from process control test strips. This saves the extra expense of having a separate densitometer in the laboratory solely for the purpose of measuring test strips. Some commercially available printers take advantage of this fact.
Currently the paper processor and printer form one unit in minilabs with the film processor separate. More recently, processing apparatus are appearing in which the film processor, printer and paper processor are integrated into one unit. This new type of apparatus are very close to true "coin-slot" operation where a non-skilled customer could simply place his film in a receptacle, place his money in the slot and then receive his prints and processed film a short while later.
In the following discussion, all examples given will refer to colour photographic systems unless otherwise stated.
Two broad types of chemical reaction take place in a photographic process, namely:
(1) those which are in some way dependent on the amount of image formed on the exposed material; and
(2) those which are independent of the amount of image formed on the exposed material.
Development is a good example of the first type of chemical reaction, and can be referred to as being "image-dependent". The amount of developer molecules used up in processing a piece of photographic material is related to the amount of latent image formed on it for given development conditions. Another example of an "image-dependent" chemical reaction is the bleaching process.
Fixing, on the other hand, is an example of an "image-independent" chemical reaction. All the silver in the photographic material is removed in a fixer bath and this amount is essentially the same regardless of the amount of exposure given to the material.
In addition, we may recognise two classes of chemical constituent of a seasoned process solution, namely:
a) those which are produced as a by-product of the reaction, such as halide ions or unreacted molecules of oxidized developer in the developer solution, and
b) those which are depleted as a result of the reaction, such as the thiosulphate ion in the fixer.
The replenishment of chemicals which are depleted in a reaction which is "image-independent" may be accomplished by a measure of the area of the photographic material being processed. This is the case with fixers where all the silver is removed from the material and is complexed with thiosulphate ion. Replenishment of thiosulphate in the fixer is easily achieved by knowing what area of film or paper has been processed and the amount of silver per unit area of the material being processed. This technique is well-known in the industry and has been used for a long time.
Current industry practice for the replenishment of developers in processing apparatus is to use a signal derived solely from
REFERENCES:
patent: 4680123 (1987-07-01), Wernicke et al.
patent: 4881095 (1989-11-01), Shidara
patent: 4988448 (1991-01-01), Woog
Bowers Jr. Charles L.
Eastman Kodak Company
Pasterczyk J.
Roberts Sarah Meeks
Tucker J. Lanny
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